The present invention relates to a method and apparatus for treating soil before planting, and more particularly to a new portable device and process for drenching soil to free it from pest and disease agents including deep dwelling nematodes before planting.
In commercial agriculture, before the planting of a crop it is usually desirable to treat the soil in order to free it from pests and disease agents that might interfere with healthy plant growth and crop production. The most notorious of these pests include soil-borne fungi, bacteria, actinomycetes, weed seeds and nematodes.
In any given cropping system one or more soil pests will gradually build in population to the point where the population levels remaining from the previous crop will not permit healthy and proper development of any newly planted crop which is also susceptible to the same pest. It is for this reason that crop rotation is an important method of soil pest control. It is for this same reason that soil fumigation has permitted growers to replant quickly after removing a previous crop.
The pests of concern are varied. They can be the relatively shallow dwelling soil fungi or bacteria which cause seedling diseases, or nematodes which are more subtle but insidious in their effect. Many times the actual disease incitant is not clearly known or is a combination of several organisms. In some cases the pest is singularly important but only in certain soil types or at certain times of the year. In the case of high value crops or nursery crops which are to be sold pest and disease free, the grower can afford to spend time and effort to rid the soil of specific pests. Examples include root knot nematodes, virus-transmitting nematodes, seedling diseases caused by pythium or rhizoctonia fungi, streptomyces scabies which causes a pox or fusarium fungus which may only be controllable before planting. All of these examples, as well as weed seeds are susceptible to treatment with certain biocides (biocidal materials) if properly delivered to their location in soil.
In the past, several volatile chemicals such as 1,3-dichloropropene and methyl bromide were used in commercial agriculture for soil treatment purposes. As a result of increasing environmental regulation, the number of currently registered chemicals available for these purposes is being greatly diminished. Because methyl bromide is highly volatile, it is almost always applied under a "gas-tight" polyethylene sheet. The sheet is laid down over the entire field after a tractor injection of the methyl bromide into the soil. As a result, methyl bromide is very expensive to use; and, according to the Clean Air Act of 1992, it is scheduled to be completely banned from use in the U.S.A. by the year 2000 because it is a class I ozone depletor.
The agricultural industry is therefore presented with a serious dilemma. On the one hand, there is an ever increasing demand for more efficient food production from land that is dedicated to agricultural use. On the other hand, there is at the same time a demand for a reduction and/or elimination of the use of volatile and toxic chemicals in food production. It is therefore not only desirable but necessary that alternative pre-planting soil treatments and methods be developed.